The field of this invention relates generally to gas turbine engine combustors, and more particularly to ferrules for mounting engine components in communication with the combustion chamber of such combustors.
Gas turbine engines such as those used as aircraft engines typically have a combustor defining an internal combustion chamber in which fuel is combusted. One or more components, including without limitation fuel nozzles and igniters, are held in communication with the internal combustion chamber by being mounted on the combustor housing by a suitable ferrule and extending through the housing into the combustion chamber. Conventional ferrules (and therefore the components mounted on the combustor by such ferrules) are commonly moveable relative to the housing to allow for tolerance stackup and thermal growth of various operating components of the engine.
An annular space or cavity within the internal combustion chamber surrounds the portion of the component that extends through the ferrule into the chamber. Due to aerodynamics within the combustion chamber, fuel can enter into this annular cavity and burn, thereby increasing the temperature of the component and increasing the risk of damage to the component and/or to the combustor housing. To this end, it is known to provide a ring of uniformly spaced and sized openings (typically referred to as purge gas openings or cooling air openings) in the ferrule at a transverse location relative to the portion of the engine component that extends into the chamber such that purge gas (usually air) flows into the combustion chamber via the purge gas openings at the annular cavity surrounding the component to purge the cavity of trapped fuel and/or to cool the component within the combustion chamber.
As the combustion chamber heats up, tolerance stackup and relative thermal growth of the various components of the combustor cause the ferrule and the component mounted thereby to move or become repositioned transversely relative to the combustor housing. Such movement results in the annular cavity surrounding the portion of the ferrule mounted component within the combustion chamber to substantially narrow along a region of the annular cavity and to substantially widen along an opposite region of the annular cavity. Along the widened region of the cavity the single ring of purge gas openings is no longer sufficient to direct enough air into the cavity to purge the cavity of trapped fuel.
There is a need, therefore, for a gas turbine engine combustor having one or more ferrules that more effectively allow for purging of trapped fuel surrounding components that are mounted by the ferrule and extend into the combustion chamber of an engine throughout the range of movement of the ferrule during operation of the engine.